复杂地形山区Landsat TM影像C校正策略与实验

采用分坡度、分NDVI（归一化差异植被指数）和分地类的C校正策略，对复杂地形山区Landsat TM影像进行地形校正，并运用视觉检验、回归分析和遥感分类精度将3种C校正策略的结果与传统的整体C校正进行对比，以探寻适合复杂地形山区的C校正策略。在此基础上，进一步探讨了地形校正对影像重采样尺度的响应。研究结果表明：与传统的整体C校正相比，采用分坡度、分NDVI和分地类的C校正策略能更好地消除原影像的凹凸感，减弱地形效应，且背阳面影像的过校正现象减少；各种C校正策略和整体C校正对Landsat TM影像不同波段的校正效果不一，其中，分地类的C校正策略对波段1、2、3和波段7的校正效果最好，分坡度的C校正策略对波段5的校正效果更佳，而整体C校正则对波段4的校正效果最好；虽然所有C校正均能有效地消除影像中的地形效应，但并未能提高影像分类精度；从不同重采样尺度C校正结果对比看，随着采样尺度增加，地形效应逐渐减弱，但并未完全消除，因此，中、低空间分辨率遥感影像的地形效应也不容忽视。

Analysis and Comparison Test on C-correction Strategies and Their Scale Effects with TM Images in Rugged Mountainous Terrain

Topographic correction for remotely sensed images is an important preprocessing step to remove the topographic effects in rugged mountainous terrain. In this study, different C-correction strategies （determining the empirical c-parameter for different NDVI intervals, different land use types, and different slope intervals） and scale levels are used to eliminate the effects of topography on Landsat TM images in complex mountains terrain. Performance of the three strategies was tested by visual comparison, correlation analysis between corrected imag-es and the solar illumination angle （cosi）, and image classification accuracy. It is attempted to find a C-correction strategy more suitable for mountainous area. The test site selected for this study is Nanting River basin, which is a subbasin of the Nujiang-Salween River. Visual comparisons showed that all the three strategies of C-correction can substantially eliminate negative terrain effects. All the C-correction strategies, similar to the global C-correc-tion, resulted in over-correction phenomenon to different degree. The landuse-specific C-correction performs best on band 1, band 2, band 3 and band 7, the global C correction performs best on the band 4, while the slope-specific C-correction performs best on band 5. To achieve the best effect, different bands can be considered to take different strategies. Although these C-correction strategies can remove negative terrain effects, classifica-tion accuracy of Landsat TM images was not improved in our pilot area. Topography obviously affects remote sensing images with high spatial resolution, however, the effects of terrain on remote sensing images with low spatial resolution cannot be ignored.